Those parts are easily removed by doing a vanilla install the first thing you do. Windows (esp 10) still had some built-in things you don't get away from though. And also all the dialogues from self-updating software and plugins.
The bigger problem, though, is all the legacy that's holding it back in the name of backwards compatibility. The WinAPI is older than myself. You can still run Windows 95 programs on your new Windows 10 PC. While useful to some, I'll never understand why exactly is it done this way. Apple keeps dropping old APIs to make their OSes better and simpler internally. I've never used anything that came before OS X, but I did read a lot that it was terrible and unstable, just like Windows at the time. Except modern macOS is stable and robust, while Windows still feels extremely fragile and unreliable after all these years.
Yes, I understand that Microsoft is hellbent that modern Windows versions need to be able to run 25-year-old binaries unmodified. But they could've achieved the exact same thing by putting genuine Windows 95 into a VM and seamlessly integrating it with the desktop.
Because they make a lot of money on enterprise customers. The only way to convince them to upgrade is to guarantee the new OS version won't break their legacy software. But even on consumer market, in the 90s and 2000s it was important old videogames work on new versions of Windows, or otherwise people would not upgrade.
This comes from before the days of web applications and everything as a Service. Software vendors had to work hard to get people to pay them again.
So Microsoft has always had to work hard to convince people to upgrade. New features were the natural way of doing that. But not maintaining backward compatibility, in a world where almost all software was an one-time purchase, would be a deal breaker. Why upgrade if it's going to cost $20M to make our ERP suite compatible with the new Windows? Why upgrade if all the software I spent $1000 on over the past few years will no longer work? Hence backwards compatibility with existing software was a top priority (to the point that Windows has a lot of fixes to badly coded third-party software built in).
Hand on heart, do you really feel OS X/macOS is improving much?
Apparently, when they run out of technical things to improve and stupid code signing policies to enforce, they redesign the UI because it's a law that if you're making a popular OS it absolutely has to have a major update once a year, no matter what.